Atomic Number: 104
Group: 4 or IV B
Atomic Weight: 261
Period: 7
CAS Number: 53850-36-5


Noble Gas
Rare Earth Element
Platinum Group Metal
No Stable Isotopes
Solid (Predicted)

Description • Uses/Function

In 1964, workers of the Joint Nuclear Research Institute at Dubna (U.S.S.R.) bombarded plutonium with accelerated 113 to 115 MeV neon ions. By measuring fission tracks in a special glass with a microscope, they detected an isotope that decays by spontaneous fission. They suggested that this isotope, which had a half-life of 0.3 ± 0.1 s might be rutherfordium-260, produced by the following reaction. Plutonium-242 collides with neon-22 yielding the daughter rutherfordium-260 and four neutrons. Element 104, the first transactinide element, is expected to have chemical properties similar to those of hafnium. It would, for example, form a relatively volatile compound with chlorine (a tetrachloride). The Soviet scientists have performed experiments aimed at chemical identification, and have attempted to show that the 0.3-s activity is more volatile than that of the relatively nonvolatile actinide trichlorides. This experiment does not fulfill the test of chemically separating the new element from all others, but it provides important evidence for evaluation. New data, reportedly issued by Soviet scientists, have reduced the half-life of the isotope they worked with from 0.3 to 0.15 s. The Dubna scientists suggest the name kurchatovium and symbol Ku for Element 104, in honor of Igor Vasilevich Kurchatov (1903—1960), late Head of Soviet Nuclear Research. The Dubna Group also has proposed the name dubnium for Element 104. In 1969, Ghiorso, Nurmia, Harris, K. A. Y. Eskola, and P. L. Eskola of the University of California at Berkeley reported they had positively identified two, and possibly three, isotopes of Element 104. The group also indicated that after repeated attempts so far they have been unable to produce isotope 260104 reported by the Dubna groups in 1964. The discoveries at Berkeley were made by bombarding a target of californium-249 with carbon-12 nuclei of 71 MeV, and carbon-13 nuclei of 69 MeV. The combination of carbon-12 with californium-249 followed by instant emission of four neutrons produced Element 104-257. This isotope has a half-life of 4 to 5 s, decaying by emitting an alpha particle into nobelium-253, with a half-life of 105 s. The same reaction, except with the emission of three neutrons, was thought to have produced Element 104-258 with a half-life of about 1/100 s. Element 104-259 is formed by the merging of a carbon-13 nuclei with californium-249, followed by emission of three neutrons. This isotope has a half-life of 3 to 4 s, and decays by emitting an alpha particle into nobelium-255, which has a half-life of 185 s. Thousands of atoms of Element 104-257 and Eleemnt 104-259 have been detected. The Berkeley group believe their identification of Element 104-258 was correct. As of January 1995 it was thought that eleven isotopes of Element 104 have been identified. The Berkeley group proposed for the new element the name rutherfordium (symbol Rf), in honor of Ernest Rutherford, New Zealand physicist. This name was formally adapted by IUPAC in 1997. 1

Physical Properties

Density:   g/cm3

* - at 1 atm

Electron Configuration

Electron Configuration: [Rn] 7s2 5f14 6d2
Block: d
Highest Occupied Energy Level: 7
Valence Electrons: 

Quantum Numbers:

n = 6
ℓ = 2
m = -1
ms = +½


Ionization Potential   eV 2  kJ/mol  
Ionization Potential   eV 2  kJ/mol  
Ionization Potential   eV 2  kJ/mol  
1 6    578.9


Nuclide Mass 3 Half-Life 3 Nuclear Spin 3 Binding Energy
253Rf 253.10069(49)# 13(5) ms (7/2)(+#) 1,867.53 MeV
254Rf 254.10018(31)# 23(3) μs 0+ 1,875.60 MeV
255Rf 255.10134(19)# 1.64(11) s (9/2-)# 1,883.67 MeV
256Rf 256.101166(26) 6.45(14) ms 0+ 1,891.74 MeV
257Rf 257.10299(11)# 4.7(3) s (1/2+) 1,899.81 MeV
258Rf 258.10349(22)# 12(2) ms 0+ 1,907.88 MeV
259Rf 259.10564(8)# 2.8(4) s 7/2+# 1,915.95 MeV
260Rf 260.10644(22)# 21(1) ms 0+ 1,924.03 MeV
261Rf 261.10877(3) 5.5(25) s 3/2+# 1,932.10 MeV
262Rf 262.10993(30)# 2.3(4) s 0+ 1,940.17 MeV
263Rf 263.11255(20)# 11(3) min 3/2+# 1,938.93 MeV
264Rf 264.11399(48)# 1# h 0+ 1,947.00 MeV
265Rf 265.11670(46)# 13 h 3/2+# 1,955.07 MeV
266Rf 266.11796(58)# 10# h 0+ 1,963.14 MeV
267Rf 267.12153(62)# 5# h [2.3(+980-17) h] 1,961.90 MeV
268Rf 268.12364(76)# 1# h 0+ 1,969.97 MeV
Values marked # are not purely derived from experimental data, but at least partly from systematic trends. Spins with weak assignment arguments are enclosed in parentheses. 3


Safety Information

Material Safety Data Sheet - ACI Alloys, Inc.

For More Information

External Links:


(1) - Lide, David R. CRC Handbook of Chemistry and Physics, 83rd ed.; CRC Press: Boca Raton, FL, 2002; p 4:27.
(2) - Lide, David R. CRC Handbook of Chemistry and Physics, 83rd ed.; CRC Press: Boca Raton, FL, 2002; p 10:178 - 10:180.
(3) - Lide, David R. CRC Handbook of Chemistry and Physics, 83rd ed.; CRC Press: Boca Raton, FL, 2002; pp 6:193, 12:219-220.
(4) - Lide, David R. CRC Handbook of Chemistry and Physics, 83rd ed.; CRC Press: Boca Raton, FL, 2002; pp 6:123-6:137.
(5) - Lide, David R. CRC Handbook of Chemistry and Physics, 83rd ed.; CRC Press: Boca Raton, FL, 2002; pp 6:107-6:122.
(6) - Atomic Mass Data Center. (accessed July 14, 2009).